1. Field of the Invention
This invention relates to a device for mixing fluids, notably liquids, and dispensing the mixture thus obtained. This invention is applicable advantageously to the mixing and dispensing of a mixture of liquid products liable to react chemically, such as polyols or liquid organic resins with isocyanates to yield polyurethane foams utilized notably for packaging purposes.
2. The Prior Art
The essential difficulty encountered with all hitherto known devices of this kind is due to the fact that, when the mixed fluids react rapidly and strongly, or are each liable to dry or harden, these devices are eventually stopped. Therefore, it is necessary to have the possibility of clearing the feed passages, the mixing chamber, the dispensing nozzle, and all the other component elements of the device that are in contact with at least one of the fluid implemented.
Many devices have already been proposed for dispensing polyurethane foam and solving the above-mentioned problem.
Thus, a device of this character is disclosed in the US-A-4 023 733 and 3 263 928, and in the FR-A-2 122 920, wherein the mixing chamber comprises a Teflon core forming a mixing bore wherein an adjustment rod is adapted to slide for closing or opening fluid inlet conduits opening into said bore. As this solution did not prove to be satisfactory per se, other additional or complementary arrangements have been proposed to avoid the unpleasant stopping or clogging effects. Thus, it is known that it is advantageous to off set longitudinally the conduits delivering the products to be mixed, to provide a solvent-filled tank at the rear of the mixing chamber, or to inject solvent or compressed air though the conduits and/or through the mixing chamber.
On the other hand, it is obvious and known that it is advantageous to have the possibility of disassembling the device, notably the mixing chamber (with or without the adjustment rod) so that this chamber can be replaced and/or cleaned when it is too much stopped (U.S. Pat. Nos. 3,263,928, 3,417,923, 3,784,110, 3,224,642, 3,291,396 and 4,469,251, and French Patent No. 2,511,889).
However, the known devices wherein the mixing chamber can be replaced are not satisfactory in actual practice for the following reasons:
when the rod is rigidly connected to the device, the chamber cannot be removed unless the rod is extracted from the support and inserted into a new chamber, an operation that can hardly be performed without damaging the new core and the rod-guiding sliding-contact bearings;
the hitherto known forms of embodiments of the releasable coupling of the mixing chamber and/or the rod with the support consisting of the device and/or the rod control means do not provide a sufficiently accurate and well-centered coupling with said support and/or the control means, thus leading to premature wear and tear of the rod and core, and damaging the connection of the fluid supply conduits of the support with those of the mixing chamber;
the hitherto known means proposed for detachably connecting the mixing chamber with the support are not strong enough and thus tend to break up before the device is fully clogged and before the mixing chamber is replaced or cleaned, so that accidents and/or a complete failure of the device or of its essential and most expensive component elements are most likely to take place;
mixing chambers, and more particularly the rods sliding in the core, are very expensive items and must be machined with a high degree of precision. Therefore, it is undesirable to provide systematically several sets of mixing chambers and/or rods;
assembling and replacement handlings are both time-robbing and tedious, thus impairing productivity, and may cause shocks, falls or stain of the mixing chamber.
When a rod detachable from the control means provided for replacing the mixing chamber, the actuation of the device when the adjustment rod is not properly associated with said control means may cause accidents or damage essential and expensive component elements of the device.
On the other hand, the Applicant found that in actual practice the clogging of the bore of the mixing chamber is a very seldom occurrence, for in the closed position, the rod clears any products left therein, and that stopping problems occur mostly only in the conduits supplying the fluid products to the support and to the mixing chamber.
Under these conditions, according to a specific feature of the present invention, and in contrast to the teachings of the prior art, it is not desirable to have the possibility of removing the mixing chamber and more particularly the means for adjusting the control means and the support, except under very exceptional circumstances, for instance when the mixing chamber is clogged completely with the products.